HTTP.sys Reason Phrases

  • Article

Applies To: Windows Server 2003, Windows Server 2003 with SP1

The following reason phrases can appear in an HTTP.sys error log file to describe the error that caused the log file entry:

Connection_Abandoned_By_AppPool

This reason phrase indicates that the error was caused by a worker process stopping unexpectedly and orphaning requests.

Connection_Dropped

This reason phrase indicates that a zombie connection was dropped by IIS and not resolved correctly.

Various connection time-out errors

These reason phrases include the following various connection time-out errors:

  • Timer_ConnectionIdle. There has been no new data sent over the connection since the last send from the client to server, and the connection timed out.

  • Timer_HeaderWait. A connection was initiated with the server, but the headers for the request were not received in a timely manner.

  • Timer_MinBytesPerSecond. The minimum throughput rate was not maintained.

  • Timer_EntityBody. The connection expired while waiting for the entity body to arrive.

  • Timer_AppPool. The connection expired because the request waited too long in an application pool queue.

Various errors

These reason phrases include the following errors, most of which are parse errors:

  • BadRequest

  • Verb

  • URL

  • Header

  • Hostname

  • Invalid_CR/LF

  • Number

  • FieldLength

  • RequestLength

  • Forbidden

  • LengthRequired

  • Precondition

  • EntityTooLarge

  • URL_Length

  • Internal

  • N/I

Internal

This reason phrase indicates that an HTTP Error 500, internal server error, occurred.

N/I

This reason phrase indicates that an HTTP Error 501, not implemented, occurred.

All 503 errors

The 503 errors are service unavailable errors. These reason phrases include the following 503 errors:

  • N/A. The service is unavailable.

  • ConnLimit. The site connection limit has been reached.

  • AppOffline. Because of rapid fail protection, the application was taken offline by IIS.

  • QueueFull. The application request queue is full.

  • Disabled. The administrator has taken the application offline.

  • AppShutdown. The application was automatically shut down because of an administrator policy.

  • AppPoolTimer. The application pool process is too busy to handle the request.

Version_N/S

This reason phrase indicates that an HTTP error 505, HTTP version not supported, occurred.